A multi-wavelength census of star formation activity in the young embedded cluster around Serpens/G3-G6

¹ Nordic Optical Telescope, Apdo 474, 38700 Santa Cruz de La Palma, Spain e-mail: amanda@not.iac.es
² CEA/DSM/DAPNIA, Service d'Astrophysique, C.E. Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette, France
³ AIM – Unité Mixte de Recherche CEA – CNRS – Université Paris VII – UMR 7158, France
⁴ Observatoire de Bordeaux, BP 89, 33270 Floirac, France
⁵ Stockholm Observatory, Roslagstullsbacken 21, 10691 Stockholm, Sweden

Received: 3 May 2006
Accepted: 6 July 2006

Abstract

Aims.The aim of this paper is to characterise the star formation activity in the poorly studied embedded cluster Serpens/G3-G6, located ~45′ (3 pc) to the south of the Serpens Cloud Core, and to determine the luminosity and mass functions of its population of Young Stellar Objects (YSOs).

Methods.Multi-wavelength broadband photometry was obtained to sample the near and mid-IR spectral energy distributions to separate YSOs from field stars and classify the YSO evolutionary stage. ISOCAM mapping in the two filters LW2 (5–8.5 μm) and LW3 (12–18 μm) of a   field was combined with JHK_S data from 2MASS, K_S data from Arnica/NOT, and  data from SIRCA/NOT. Continuum emission at 1.3 mm (IRAM) and 3.6 cm (VLA) was mapped to study the cloud structure and the coldest/youngest sources. Deep narrow band imaging at the 2.12 μm S(1) line of H₂ from NOTCam/NOT was obtained to search for signs of bipolar outflows.

Results.We have strong evidence for a stellar population of 31 Class II sources, 5 flat-spectrum sources, 5 Class I sources, and two Class 0 sources. Our method does not sample the Class III sources. The cloud is composed of two main dense clumps aligned along a ridge over ~0.5 pc plus a starless core coinciding with absorption features seen in the ISOCAM maps. We find two S-shaped bipolar collimated flows embedded in the NE clump, and propose the two driving sources to be a Class 0 candidate (MMS3) and a double Class I (MMS2). For the Class II population we find a best age of ~2 Myr and compatibility with recent Initial Mass Functions (IMFs) by comparing the observed Class II luminosity function (LF), which is complete to 0.08 , to various model LFs with different star formation scenarios and input IMFs.